Just a quick thought... When you're talking about an 80 gram weight loss it could very well be the difference between him being fed before being weighed the first time and then the second time being a couple of hours after a feed.

I think it is a great sign that his nappies are on track and he is alert etc. My DS was very slow to gain weight in the first month or so, so we were waking him every 3 hours overnight to feed, once his weight gain got on track we stretched it out to four hours, then six and then let him go for as long as he could. That said I kept up a 10pm dream feed until he was 7 or 8 months. TBH I would be concerned about him only having one feed in 15 hours... Personally (and I'm definately no expert, just a BF'ing mum) I would try doing a dream feed before you go to bed for a few days, if it works great, and if doesn't you really haven't lost anything.